David. Honestly, the iron heads will make the sought after power. There drawbacks are;
Heavy & Low flow
Also, in a large engine like your doing, the head will choke the performance of the engine in power and RPMs. But you will make the power you listed above. 350hp is something you would have to be deaf dumb and blind to miss.
Depending on what your starting with, it could be cost effective to upgrade them, to a certain point that is.
I would be amazed if you found “Ready to Run” X heads at a reasonable cost. Or even cost effective vs aluminum heads.
Thanks
@sport74 And speaking of the show, Dave’s mentioning of cylinder heads, he says, and I agree, “Afford the best cylinder head you can.”
